The present invention relates to a method of manufacturing a semiconductor device having a reinforcing member and a method of manufacturing an IC card or smart card using the device and, more particularly, to a method of manufacturing a semiconductor device having a reinforcing member which is bonded to the lower surface of an IC chip and a method of manufacturing an IC card using the device.
For example, a telephone card conventionally used for a public telephone generally uses a magnetic card. However, a magnetic card stores only a small amount of information and cannot cope with various new services. Hence, use of an IC card has been examined.
An IC card currently under development has a structure as shown in FIG. 5. An integrated circuit chip (to be referred to as an IC chip hereinafter) 6 is mounted on an IC card substrate 10 by the flip chip bonding. An electrode 6a for transmitting/receiving a signal to/from an external device is formed on the lower surface of the IC card substrate 10. The structure on a bump 8 side where an integrated circuit is formed is encapsulated with an underfill resin 9 to construct a module. This module is mounted in a card main body comprised of card bases 11, 12, and 13, so an IC card 14 is formed as a whole.
In an IC card, an IC chip storing various data is buried in a resin card. Additionally, an electrode or coil connected to the buried IC chip is formed on the card surface. The IC card has a function of allowing a data read/write from/into an external device via an electrode formed on the card surface in a contact or non-contact state. The IC card having this structure is highly secure because data is converted into an electrical signal and stored in the internal IC chip. Also, a larger quantity of information can be stored and held. These advantages cannot be attained by a magnetic card.
Many IC cards have card bases formed from a plastic material such as PET (polyethylene terephthalate) or vinyl chloride. The IC chip incorporated in the IC card is buried in the card bases and protected from external humidity.
Many IC cards have a thickness of about 0.76 mm in consideration of portability. An IC-card-type telephone card that NTT (Nippon Telegraph and Telephone Corp.) is planning to issue is expected to have a thickness of about 0.5 mm. A 0.25-mm thick IC card thinner than the 0.5-mm thick card has also been under development.
As described above, the thickness of IC cards tends to be smaller year by year. As IC cards become thin, IC chips incorporated in the IC cards must also be thinner. For, e.g., a 0.76-mm thick IC card, the incorporated IC chip has a thickness of about 0.2 to 0.25 mm. For a 0.25-mm thick IC card, the IC chip must also be as thin as 0.05 mm.
However, when IC chips become thin, wafers or IC chips may break during the process of manufacturing IC chips in a wafer state or the process of mounting an IC chip cut from a wafer, so the wafers or IC chips are unusable at high probability. Hence, as IC chips become thin, the yield in the IC chip mounting process becomes low. In addition, since thin wafers or IC chips are processed, they must be carefully handled in various operations during the IC chip manufacturing and mounting processes, resulting in low operation efficiency and low productivity.
When IC chips are thin, the durability of IC cards readily degrades. As far as a card incorporating a thin IC chip is thick, the card cannot be easily intentionally bent, and no stress is applied to the IC chip in the IC card. However, an IC chip is made thin in order to reduce the thickness of an IC card. A thin IC card itself readily bends, and bending stress is easily applied to the IC chip. An IC chip easily bends as it becomes thinner. In comparison between silicon used for an IC chip and a polymer material such as PET used for a card base, silicon cannot easily bend, and the IC chip readily breaks.
To improve the durability of the thin IC cards, various measures have been conventionally taken to protect thin-film IC chips in IC cards. For example, in a technique disclosed in Japanese Patent Laid-Open No. 3-158296, a structure has been proposed, in which a reinforcing member is attached to an IC chip, and the IC chip is fixed on the mounting substrate through the reinforcing member. In a technique disclosed in Japanese Patent Laid-Open No. 8-324166 as well, an IC module structure has been proposed, in which a reinforcing member is attached in advance to a surface different from the terminal surface of an IC chip.
To attach a reinforcing member to an IC chip, conventionally, a reinforcing member having the same size as that of a divided IC chip is bonded to each of the divided IC chips. However, this method increases the process time and cost. Japanese Patent Laid-Open No. 9-263082 discloses a method of shortening the reinforcing member bonding time.
In the technique disclosed in Japanese Patent Laid-Open No. 9-263082, after a wafer on which IC chips are formed is divided into chips, the divided chips are fixed on a transfer sheet while maintaining the wafer shape. Reinforcing members arrayed and divided in advance as in chips are fixed on another transfer sheet. The two transfer sheets are overlaid and bonded. According to this method, since the reinforcing members can be simultaneously bonded to a plurality of IC chips, the bonding time can be shortened. In mounting, since an IC chip to which a reinforcing member has already been attached is used, even the thin-film chip can be easily handled in the mounting process.
However, in the method disclosed in Japanese Patent Laid-Open No. 9-263082, positioning is necessary when the transfer sheets are overlaid. If positioning fails, many IC chips become defective at once to result in large loss, which suffers a new problem. For accurate positioning, an overlay apparatus with a new positioning mechanism must be used in addition to a conventional mounting apparatus, resulting in an increase in facility cost.